Green Bay Packers quarterback Aaron Rodgers (12) is hit by Detroit Lions linebacker Landon Johnson in the first half of an NFL football game Sunday, Dec. 12, 2010 in Detroit. Rodgers left the game and did not return. The Lions defeated the Packers 7-3. (AP Photo/Duane Burleson)

GREEN BAY, Wis. (AP) — Even with Green Bay's playoff hopes in jeopardy, coach Mike McCarthy insists the team will err on the side of caution when evaluating Aaron Rodgers' second concussion of the season.

Rodgers was expected to begin the evaluation protocol for head injuries Monday. The quarterback's availability for Sunday's game at New England remains unclear.

"We're not going to take any chances," McCarthy said. "No different than on game day. When it became a question, an issue — was he clear, wasn't he clear? — we pulled him immediately. We'll always take the high side of caution in these types of situations."

Rodgers left Sunday's game at Detroit shortly after he was hit hard on back-to-back plays in the second quarter, a scramble and a sack. He was replaced by Matt Flynn, and the Packers went on to lose 7-3.

Rodgers also sustained a concussion in Green Bay's loss at Washington on Oct. 10. He played against Miami the following week and has not missed a game since taking over as the Packers' starter in 2008.

Going into Sunday's game at New England, McCarthy said doctors will consider Rodgers' recent concussion as they evaluate him.

"He's just getting ready to start to go through the first procedure, first process of the testing and so forth," McCarthy said Monday. "They had him sleep in this morning, and I just had a chance to visit with him. We'll go through the protocol that we do with all of our players, and we'll probably have a little better update for you Wednesday or Thursday."

According to NFL guidelines for head injuries, Rodgers must be symptom-free and cleared by a team doctor and independent neurological consultant before he can play again.

Rodgers' situation isn't the only bad injury news for the Packers this week.

McCarthy said Green Bay could be without outside linebacker Frank Zombo on Sunday because of a sprained knee. And defensive end Cullen Jenkins, who sat out Sunday's game with a calf injury, isn't expected back this week, either.

McCarthy said left guard Daryn Colledge has a chance to play Sunday after spraining his knee against the Lions.

But the team's biggest concern by far will be Rodgers.

"We've got to make sure, No. 1, that Aaron is healthy and take care of him," wide receiver Greg Jennings said after Sunday's game. "He's the priority. Health is first and foremost. You can't risk it all because you want to play a game. We understand that. As an offense, we just have to come together and refocus and rededicate ourselves on the practice field."

Rodgers is well on his way to becoming one of the league's elite quarterbacks, but still needs to learn to slide out of danger when he takes off running.

"We probably need to do a better job of getting that across because the quarterbacks can't be taking unnecessary hits like that," McCarthy said.

Facing significant pass rush pressure from the Lions, Flynn was 15 of 26 for 177 yards with an interception in relief of Rodgers. Flynn said he'll be ready if Rodgers can't play Sunday.

"We'll see what happens, but I'm going to prepare the hardest I've ever prepared," Flynn said. "Because obviously I made a couple of mental mistakes that shouldn't happen, especially in tough situations when those things can't happen."

Linebacker Clay Matthews said the Packers have been dealing with injuries all season and will handle Rodgers' absence if they have to.

"We hope we have Aaron back; he's a special athlete," Matthews said. "But at the same time, this has been the story of the Green Bay Packers this year — having guys step up. We've been able to play with the players we have and do a good job."